1. Field of the Invention
The present invention relates to a control apparatus and method for an engine-motor hybrid vehicle, and more particularly to a control apparatus and method, which has a function of operation compensation of a power transmission device.
2. Description of Related Art
Various engine-motor hybrid vehicles having an engine, a storage battery, and a power or energy transmission device for transmitting energy among the engine, storage battery and a vehicle drive shaft are known.
When an engine is operated at an operation point within a highest operation efficiency region, that is, a large torque and low rotation speed region, the engine tends to produce periodic vibration in the idling operation region. In JP-A-9-201005, therefore, the engine is operated in a small torque and high rotation speed region, which is outside of the highest operation efficiency region, when the engine is in the idling region. This shifting of the operation point from the highest operation efficiency region to the other region will lessen the fuel consumption efficiency. In JP-A-63-167640, a periodic change is applied to an alternator output in the opposite phase relation with a periodic change in an engine.
It is also known that the power transmission device can be two rotary electric machines. In JP-A-7-135701, the rotary electric machines are controlled with respect to rotation speed and torque, respectively, to use the output torque of the engine directly as the driving power for the vehicle. In DE 4407666A1, the rotary electric machines are used to transmit the output torque of the engine electromagnetically and assist the torque, respectively. In the hybrid vehicles having those kinds of power transmission devices, controllability is lessened and audible noise is increased at the time of high speed operations or transient operations.
Further, in JP-A-9-170533, one of the two rotary electric machines is used to operate the engine at engine starting. In JP-A-9-117012, one of the two rotary electric machines is used to operate the engine after raising the engine rotation speed above the idling speed, requiring a large amount of electric power from the storage battery. In a rotation control motor and torque assist motor type power transmission device, the engine is operated at a fixed torque at the time of engine starting. Upon shifting from the fixed torque to the rotation speed control, mechanical shocks arise and are transmitted.